ARM: 7579/1: arch/allow a scno of -1 to not cause a SIGILL

On tracehook-friendly platforms, a system call number of -1 falls through without running much code or taking much action. ARM is different. This adds a short-circuit check in the trace path to avoid any additional work, as suggested by Russell King, to make sure that ARM behaves the same way as other platforms. Signed-off-by: Kees Cook <[email protected]> Acked-by: Will Drewry <[email protected]> Reviewed-by: Will Deacon <[email protected]> Signed-off-by: Russell King <[email protected]>
davidwilde · Nov 19, 2012 · ad75b51 · ad75b51
1 parent 9b790d7
commit ad75b51
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
@@ -448,7 +448,10 @@ __sys_trace:
 	ldmccia	r1, {r0 - r6}			@ have to reload r0 - r6
 	stmccia	sp, {r4, r5}			@ and update the stack args
 	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
-	b	2b
+	cmp	scno, #-1			@ skip the syscall?
+	bne	2b
+	add	sp, sp, #S_OFF			@ restore stack
+	b	ret_slow_syscall
 
 __sys_trace_return:
 	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0